Add the fairings or not???

That gap is like HUGE.

It may have been either for comfort riding or flatbed work carrying front overhang.

Another possible reason is to someday build a large car apartment on that frame etc when retiring.

 

Ya don't waste you money on fairing with that gap. Nice looking truck though!!! Could be something wrong with it i'd put my money into checking the motor out instead of ugly fairings that wont help.

 

What is the rear end ratio?

 

If you own the trailer put on a nose cone. With over 3ft gap you are not going to help with a fairing. I consistently get 5mpg running the speed limit or thereabouts, loaded most of the time with much worse aerodynamics than you have, I guess you have some issues with your tractor. Charge air cooler leak, high rolling resistance tires, tire pressure low, overhead not set correctly, consistently running 70 plus. Could be all or none, but something is wrong someplace.

 

5 mpg for a modern 13 litre motor is terrible fuel economy unless you are running over 80,000 lbs gross in the mountains all day long. You should likely spend some money having the motor checked out before dropping cash on plastic fairings.

I'm driving a 2016 VNL670 with D13/iShift and pulling a 48' tandem flatdeck. Over two months and my average fuel economy is 5.8 mpg. This includes running a bunch of BC, some winter fuel already, idling overnight for A/C (for at least 8 or 9 days) and a couple oversize loads (including a 12 foot wide one).

 

Yes, that tractor was not spec'd to pull a van. That's either a deck truck or a dry/liquid bulk tanker truck. That frame stretch does you no favours outside of weight distribution.

Your truck has a 3.90-3.91 rear end ratio.



Most Super-B trucks in Canada run 3.90-3.93 and they gross 139,900 lbs and don't run much past 62-65 mph.

 

Based on what criteria did you buy this truck?